const fs = require('fs');
//改造现有异步函数api 让其返回promise对象 从容支持异步函数语法
const promisify = require('util').promisify;
//调用promisify方法改造现有异步apl 让其返回promise对象
const readFile = promisify(fs.readFile);

async function run() {
    let r1 = await readFile('./1.txt', 'utf8')
    let r2 = await readFile('./2.txt', 'utf8')
    let r3 = await readFile('./3.txt', 'utf8')
    console.log(r1);
    console.log(r2);
    console.log(r3);

}
run();